1. Field of the Invention
The present invention relates to an image display device that displays input images, and more particularly, to an apparatus and method for controlling Hue and luminance of input images depending on color gamut that can be displayed in the image display device.
2. Description of the Related Art
With development of electronics, information provided to a user includes various multimedia information as well as simple text information. The multimedia information includes various formats such as still images, moving images, animation, sound, and the like. Particularly, of the multimedia information, the moving images are based on video on demand (VOD) service or interactive service. Therefore, studies of the standard related to the moving images are actively being carried out.
With development of digital electronics, conventional analog data have been digitalized. Various digital image processing technologies have been developed to efficiently process such huge data. The digital image processing technologies have the following advantages.
First, noise is included in the original signals of all the analog devices when some function is carried out. Therefore, after the noise is processed, images displayed by the finally recorded result may be degraded. However, the digital image processing device prevents the images from being degraded.
Second, since signals are digitalized, signal processing can be made based on computer. As a result, it is possible to compress image data.
The digital image processing technology is directed to how to display analog results recorded in a medium using a computer. Digital images have been embodied through a digital video interactive (DVI) method suggested since the latter half of 1980 by RCA research members. The DVI method is to implement a function, which is difficult to be processed in real time using a general processor, using a specific processor that implements a command suitable for microprogrammable image processing.
Furthermore, two experts groups of junction pictures experts group (JPEG) and motion pictures experts group (MPEG) handled since 1989 have determined a standard coding method which is difficult to be implemented in hardware but has more excellent performance than the DVI method. Such a coding method is expected to carry out a main role in development of digital images in the future because most of business entities support the coding method. Particularly, in case of the MPEG standard, the standards such as MPEG II and MPEG III have been developed for the purpose of digitalization of a high definition system such as HDTV as well as image processing for personal computers.
Moreover, technology that processes images using a main processor only without separate hardware has been introduced since 1991. Examples of such technology include QuickTime by Apple, Video for Windows by Microsoft, and Indeo by Intel Corporation. Such image processing technology has received much attention in a personal computer owing to a main processor that requires high speed.
Standardized work is also carried out with introduction of various digital image processing technologies. In accordance with such standardized work, the digital image processing technologies are not limited to the image conference system, the digital broadcasting codec system and the image telephone technology but widely compatible with computer industries and communication industries. For example, the digital image compression technology that stores data in either an optical disk such as CD-ROM or a digital recording medium is implemented by the technology almost the same as the compression technology for image communication. At present, the standardization of MPEG is handled by ISO-IEC, JTC1, SC1, and WG11, and the standardization work is in progress until now after starting of the experts groups in the 1990's.
However, image signals according to the related art are processed in three-dimensional color spaces of red (R), green (G), and blue (B) and are displayed using a light source of three colors. This is because that the three colors of R, G, and B are primary colors constituting all the colors.
Generally, a display based on a light source of three colors of R, G, and B displays all the colors using combination of R, G, and B. In this case, it is insufficient to display a synthetic color on color coordinates using R, G, and B. This is because that a color gamut actually visible to ordinary sight is greater than a color gamut of R, G, and B. Therefore, if a color other than three colors of R, G and B is added to display colors visible to ordinary sight well, it is possible to display more natural colors.
FIG. 1 illustrates the relation among primary colors used to display colors. Referring to FIG. 1, all the color signals can be displayed by combination of three primary colors of R, G and B. In this case, if a color signal R is mixed with a color signal G, a color signal Y(Yellow) is obtained. If the color signal G is mixed with a color signal B, a color signal C(Cyan) is obtained. If the color signal B is mixed with the color signal R, a color signal M(Magenta) is obtained. If the primary colors of R, G and B are mixed with one another, a white color signal W is obtained.
FIG. 2 illustrates color coordinates. FIG. 2 illustrates a color coordinate sRGB suggested in the HDTV standard, a color coordinate 3P DLP (Digital Light Processing) of a TV currently selling in the market, and a color coordinate 5P DLP of an image display device driven by five colors. The color coordinates shown in FIG. 2 have different formats from one another. That is, a color gamut;(corresponding to the color coordinate suggested in the HDTV standard) of a signal input to the image display device is different from color gamuts (corresponding to the color coordinate currently selling in the market and the color coordinate of the image display device driven by five colors) that can be displayed in the image display device.
FIG. 3 illustrates the signal input to the image display device and the signal that can be processed in the image display device. Particularly, FIG. 3 illustrates luminance and hue of a signal having the maximum chromaticity for each signal. As shown in FIG. 3, luminance and hue of the signal input to the image display device do not coincide with luminance and hue of the signal that can be displayed in the image display device. Therefore, it is required to convert luminance and hue of the signal input to the image display device into the range of chromaticity and hue of the signal that can be displayed in the image display device.